1. Field of the Invention
This invention relates to a magnetoresistive effective type element, particularly usable as a reading element of a thin film magnetic head, and the thin film magnetic head, a magnetic head device and a magnetic disk driving device which use the magnetoresistive effective type element.
2. Related Art Statement
A given information is stored in a magnetic recording medium by utilizing the direction of magnetization thereof. Then, with the recent advance of high recording density for the magnetic recording medium, such an attempt is made as to narrow the track width of the recording medium and thus, develop the longitudinal recording density thereof. Therefore, it is desired that a high sensitivity sensor to read the information precisely from the magnetic recording medium is developed. As such a sensor, recently, a thin film magnetic head including a giant magnetoresistive effective type element is utilized.
As the magnetoresistive effective type element, conventionally, a current in plane (CIP) type element was employed. According to the CIP type element, the change in sense current flown through the magnetoresistive effective film of the element itself is detected and thus, a given information stored in a magnetic recording medium is read out.
On the other hand, with the develop of longitudinal recording density by the narrowing of track width, as mentioned above, a current perpendicular to plane (CPP) type element has been employed. According to the CPP type element, the change in sense current flown perpendicular to the magnetoresistive effective film of the element itself is detected and thus, a given information stored in a magnetic recording medium is read out.
A method for flowing a current perpendicular to a magnetoresistive effective film is disclosed in National Publication of the Japanese-translated version No. 11-509956 where leading films are provided so as to sandwich the magnetoresistive effective film and the current is flown in the direction perpendicular to the magnetoresistive effective film via the leading films.
In the above method, however, it is required that shielding films are provided outside the leading films, respectively, and gap films made of insulating material are provided between the shielding films and the leading films, respectively, in order to separate the shielding film and the leading films electrically. In this case, the reading width for a magnetic recording medium depends on the distance between the shielding films, and thus, the reading width is increased and the precise reproduction of a given information stored in the recording medium can not be performed.
In this point of view, such a technique is disclosed in U.S. Pat. No. 6,084,752 as doubling shielding films of a magnetoresistive effective element as leading films thereof, and flowing a current perpendicular to the magnetoresistive effective type film via the leading films. In this case, since it is not required that other leading film are provided, in addition to the shielding films, the reading width defined by the distance between the shielding films can be reduced. However, an external noise is superimposed on a given reproduction information from the magnetic recording medium, and as a result, the magnetoresistive effective type element and thus, the thin film magnetic head results in generating larger noises.
It is an object of the present invention to provide a new CPP type magnetoresistive effective type element which can reproduce a given information stored in a magnetic recording medium at a higher S/N ratio almost without external noise.
For achieving the above objects, this invention relates to a magnetoresistive effective type element, including:
a magnetoresistive effective film,
a first shielding film of which one main surface is adjacent to one main surface of the magnetoresistive effective film,
a second shielding film of which one main surface is adjacent to the other main surface of the magnetoresistive effective film, and
a third shielding film of which one main surface is adjacent to the other main surface of the first shielding film or the second shielding film opposite to the magnetoresistive effective film and which is provided via an electrical high resistivity member,
the first shielding film and the second shielding film functioning as current-supplying layers to flow current perpendicular to and through the magnetoresistive effective film.
The inventors have intensely studied to achieve the above object. Then, they have investigated variously, in order to find out the cause of the external noise in the magnetoresistive effective type element disclosed in U.S. Pat. No. 6,084,752.
As a result, they found out that the external noise results from an external noise on a reproduction wave from the shielding films doubling as the leading films. That is, since the shielding films functions as an antenna and also, doubles as the leading films, an external noise is easily superimposed on the reproduction wave from the shielding films.
According to the present invention, since another shielding film is provided outside a shielding film doubling as a leading film via an electrical high resistivity member, the shielding effect can be maintained sufficiently for an external noise.
According to the present invention, therefore, since the reading width is determined on the distance between the first shielding film and the second shielding film which double as leading films and are provided so as to be adjacent to the magnetoresistive effective film, the reading width can be narrowed. Moreover, the third shielding film and the fourth shielding film enable a sufficient shielding effect to be imparted to the magnetoresistive effective type element of the present invention.